PUBLIC MARKS with tag sable

The weight and pressure distribution within a pile of any granular material is determined by the way in which the individual grains contact each other and distribute the stress. Quite commonly, grain shapes and sizes mean that there are microscopic chains and networks of grains that are oriented and in contact with each other in such a way that they carry most of the pressure from the weight of the material above them. These chains seem to behave like the soaring arches of Gothic cathedrals, which serve to transmit the weight of the roof, perhaps a great dome, outward to the walls, which bear the load. In a sand pile, particularly one that is confined in a container of some sort, these chains perform the same function—they carry the stress outward to the container, rather than directly downward to the base of the pile.

For an ambitious landscape design project, Magnus Larsson, a student at the Architectural Association in London, has proposed a 6,000km-long wall of artificially solidified sandstone architecture that would span the Sahara Desert, east to west, offering a combination of refugee housing and a "green wall" against the future spread of the desert.